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| Titel |
Ground-based aerosol characterization during the South American Biomass Burning Analysis (SAMBBA) field experiment |
| VerfasserIn |
J. Brito, L. V. Rizzo, W. T. Morgan, H. Coe, B. Johnson, J. Haywood, K. Longo, S. Freitas, M. O. Andreae, P. Artaxo |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 22 ; Nr. 14, no. 22 (2014-11-18), S.12069-12083 |
| Datensatznummer |
250119165
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| Publikation (Nr.) |
 copernicus.org/acp-14-12069-2014.pdf |
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| Zusammenfassung |
This paper investigates the physical and chemical characteristics of
aerosols at ground level at a site heavily impacted by biomass
burning. The site is located near Porto Velho, Rondônia, in the
southwestern part of the Brazilian Amazon rainforest, and was selected
for the deployment of a large suite of instruments, among them an
Aerosol Chemical Speciation Monitor. Our measurements were made
during the South American Biomass Burning Analysis (SAMBBA) field
experiment, which consisted of a combination of aircraft and ground-based measurements over Brazil, aimed to investigate the impacts of
biomass burning emissions on climate, air quality, and numerical
weather prediction over South America. The campaign took place
during the dry season and the transition to the wet season in
September/October 2012.
During most of the campaign, the site was impacted by regional
biomass burning pollution (average CO mixing ratio of
0.6 ppm), occasionally superimposed by intense (up to
2 ppm of CO), freshly emitted biomass burning
plumes. Aerosol number concentrations ranged from ~1000 cm−3 to peaks of up to 35 000 cm−3 (during biomass burning (BB) events, corresponding to an average
submicron mass mean concentrations of 13.7 μg m−3
and peak concentrations close to 100 μg m−3. Organic
aerosol strongly dominated the submicron non-refractory composition,
with an average concentration of 11.4 μg m−3. The
inorganic species, NH4, SO4, NO3, and Cl,
were observed, on average, at concentrations of
0.44, 0.34,
0.19, and 0.01 μg m−3,
respectively. Equivalent black carbon (BCe)
ranged from 0.2 to
5.5 μg m−3, with an average concentration of
1.3 μg m−3. During BB peaks, organics accounted for
over 90% of total mass (submicron non-refractory plus
BCe), among the highest values described in the
literature.
We examined the ageing of biomass burning organic aerosol (BBOA)
using the changes in the H : C and O : C
ratios, and found that throughout most of the aerosol processing
(O : C ≅ 0.25 to O : C ≅ 0.6), no
remarkable change is observed in the H : C ratio
(~1.35). Such a result contrasts strongly with previous
observations of chemical ageing of both urban and Amazonian biogenic
aerosols. At higher levels of processing (O : C > 0.6),
the H : C ratio changes with
a H : C / O : C slope of −0.5, possibly
due to the development of a combination of BB
(H : C / O : C slope = 0) and
biogenic (H : C /O :C slope =−1)
organic aerosol (OA). An analysis of the ΔOA /ΔCO mass ratios
yields very little enhancement in the OA loading with atmospheric
processing, consistent with previous observations. These results
indicate that negligible secondary organic aerosol (SOA) formation
occurs throughout the observed BB plume processing, or that SOA
formation is almost entirely balanced by OA volatilization.
Positive matrix factorization (PMF) of the organic aerosol spectra
resulted in three factors: fresh BBOA, aged BBOA, and low-volatility oxygenated organic aerosol (LV-OOA). Analysis of the diurnal
patterns and correlation with external markers indicates that during
the first part of the campaign, OA concentrations are impacted by
local fire plumes with some chemical processing occurring in the
near-surface layer. During the second part of the campaign,
long-range transport of BB plumes above the surface layer, as well
as potential SOAs formed aloft, dominates OA concentrations at our
ground-based sampling site.
This manuscript describes the first ground-based deployment of the
aerosol mass spectrometry at a site heavily impacted by biomass
burning in the Amazon region, allowing a deeper understanding of
aerosol life cycle in this important ecosystem. |
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